package 力扣;

import java.util.ArrayList;
import java.util.List;

/**
 给定一个包含 m x n 个元素的矩阵（m 行, n 列），请按照顺时针螺旋顺序，返回矩阵中的所有元素。
     示例 1:
     输入:
     [
     [ 1, 2, 3 ],
     [ 4, 5, 6 ],
     [ 7, 8, 9 ]
     ]
     输出: [1,2,3,6,9,8,7,4,5]
     示例 2:

     输入:
     [
     [1, 2, 3, 4],
     [5, 6, 7, 8],
     [9,10,11,12]
     ]
     输出: [1,2,3,4,8,12,11,10,9,5,6,7]
 */
public class _54螺旋矩阵 {
    // 注意点: 从右往左,和 从下往上 需要判断边界
    public List<Integer> spiralOrder(int[][] matrix) {

        List<Integer> order = new ArrayList<Integer>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return order;
        }
        int rows = matrix.length, columns = matrix[0].length;
        int left = 0, right = columns - 1, top = 0, bottom = rows - 1;
        while (left <= right && top <= bottom) {
            for (int column = left; column <= right; column++) {
                order.add(matrix[top][column]);
            }
            for (int row = top + 1; row <= bottom; row++) {
                order.add(matrix[row][right]);
            }
            if (left < right && top < bottom) {
                for (int column = right - 1; column > left; column--) {
                    order.add(matrix[bottom][column]);
                }
                for (int row = bottom; row > top; row--) {
                    order.add(matrix[row][left]);
                }
            }
            left++;
            right--;
            top++;
            bottom--;
        }
        return order;

    }
}
